The present invention relates in general to a photosensitive composition and a color paste for making the photosensitive composition. More particularly, it relates to a photosensitive composition which is advantageously used for forming a color filter of color liquid crystal display devices.
Photosensitive compositions for manufacture of a color filter array include photoresists for the three primary colors—red, green and blue, and black photoresist for black matrix that surrounds color pixels for improving color contrast. Since the composition is required to have high sensitivity, adhesion to the substrate, chemical resistance and the like, a negative radiation sensitive composition is generally used.
To produce a color filter from a photosensitive composition, a black photoresist is first applied to the surface of a substrate and dried, and then exposed to radiation through a photomask and developed to dissolve unexposed portions with an alkali developer, thereby forming a pixel pattern, the so called black matrix. These steps are repeated for the red, green, and blue photoresists, thereby completing a color filter array.
The negative photosensitive composition generally includes a pigment dispersed in a photosensitive resin system which comprises a resin having an acid functional group such as (meth)acrylic acid, a polyfunctional monomer such as pentaerythritol tri(meth)acrylate, and a photoinitiator such as 1-hydroxycyclohexylphenyl ketone.
When a color filter is formed from such a negative photosensitive composition, however, the following problems arise: (1) an undissolved product (residue or scum) of the composition may remain in unexposed portions during developing, (2) the surface of the color filter is roughened, and (3) having film-lost during developing with the alkali developer. As a result, it is difficult to produce a high-resolution pixel array with sufficient color strength. Thus, an improved photosensitive composition for a color filter is called for.